The Mosasaurinae are a subfamily of

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Ma ...

s, a diverse group of Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

marine

squamates Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles, comprising lizards, snakes, and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,900 species, it ...

. Members of the subfamily are informally and collectively known as "mosasaurines" and their fossils have been recovered from every continent except for

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

. The lineage first appears in the

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded ...

and thrived until the K-Pg mass extinction at the end of the

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...

. They ranged in size from some of the smallest known mosasaurs ('' Carinodens'', 3–3.5 meters), to medium-sized

taxa In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

('' Clidastes'', 6+ meters), to the largest of the mosasaurs ('' Mosasaurus hoffmannii'') potentially reaching about 13 m in length. Many genera of mosasaurines were either piscivorous or generalists, preying on

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% ...

and other marine reptiles, but one lineage, the Globidensini, evolved specialized crushing teeth, adapting to a diet of

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttle ...

s and/or marine

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked ...

s. Though represented by relatively small forms throughout the

and

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. ...

, such as '' Clidastes'', the lineage diversified during the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

and had by the

grown into the most diverse and species-rich mosasaur subfamily. The etymology of the group derives from the genus ''Mosasaurus'' (

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

''Mosa'' = "

Meuse river The Meuse ( , , , ; wa, Moûze ) or Maas ( , ; li, Maos or ) is a major European river, rising in France and flowing through Belgium and the Netherlands before draining into the North Sea from the Rhine–Meuse–Scheldt delta. It has a ...

" +

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''sauros'' = "lizard").

Description

Russell (1967, pp. 123–124) defined the Mosasurinae as differing from all other mosasaurs as follows: "Small rostrum present or absent anterior to

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...

ry teeth. Fourteen or more teeth present in

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

and

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The ...

. Cranial nerves X, XI, and XII leave lateral wall of opisthotic through two foramina. No canal or groove in floor of basioccipital or basisphenoid for basilar artery. Suprastapedial process of

quadrate Quadrate may refer to: * Quadrate bone * Quadrate (heraldry) * Quadrate lobe of liver * Quadrate tubercle The quadrate tubercle is a small tubercle found upon the upper part of the femur. It serves as a point of insertion of the quadratus femori ...

distally expanded. Dorsal edge of surangular thin lamina of bone rising anteriorly to posterior surface of coronoid...At least 31, usually 42–45 presacral

vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

present. Length of presacral series exceeds that of postsacral, neural spines of posterior

caudal Caudal may refer to: Anatomy * Caudal (anatomical term) (from Latin ''cauda''; tail), used to describe how close something is to the trailing end of an organism * Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into the ...

vertebrae elongated to form distinct fin. Appendicular elements with smoothly finished articular surfaces, tarsus and carpus well ossified." In his 1997 revision of the

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...

of the Mosasauroidea, Bell (pp. 293–332) retained the Mosasaurinae as a clade, though he reassigned Russell's tribe Prognathodontini to the Mosasaurinae and recognized a new tribe of mosasaurines, the Globidensini. The subfamily is generally recognised as containing two subdivisions, the tribes Globidensini ('' Globidens'' and its closest relatives) and Mosasaurini (''

Mosasaurus ''Mosasaurus'' (; "lizard of the Meuse River") is the type genus (defining example) of the mosasaurs, an extinct group of aquatic squamate reptiles. It lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages ...

'' and its closest relatives). A third tribe, the Prognathodontini ('' Prognathodon'' and its closest relatives, such as '' Plesiotylosaurus''), is also used on occasion. "Clidastini" or the adjective "clidastine" is also used sometimes, but generally refers to an adaptive grade close to and containing the genus '' Clidastes'', rather than an actual clade.

Relationships

Cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

of the Mosasaurinae modified from Simões et al. (2017):

Description

Relationships

References

Further reading